The experiments encompassed in this proposal will examine the cytological organization of the human and non-human primate placenta and fetal membranes by correlated transmission electron microscopy (TEM), scanning electron microscopy (SEM), and freeze-fracture (F0F) methods. The structural organization of freeze-fracture trophoblast cell membrane will be analyzed to determine the normal size, number and distribution of intramembranous particles. Changes in cell membrane organization with increasing gestational age will also be studied. The number and distribution of anionic sites, Con A receptor sites and immunoglobulin receptor sites will be analyzed by correlated SEM and TEM utilizing probes which can be directly or indirectly observed in the EM. Changes in receptor site distribution under the influence of various metabolic inhibitors and disruptors of cytoskeletal elements in the underlying cytoplasm will also be examined. Membrane specializations associated with internatization of cell membrane receptors during endocytosis will be studied by TEM and F-F methods. The effect of metabolic inhibitors and disruptors of cytoskeletal elements on endocytosis and intracellular movement of endocytic vesicles will be studied by EM and quantitative (rocket) immunoelectrophoresis. The cytological basis of fetal placental capillary permeability will be studied in non-human primate and guinea pig placentas using electron-dense tracer probes. The cytological organization of amnion cell membrane structure and amniotic epithelial permeability will be studied using TEM, SEM and F-F techniques as well as electron dense probes of epithelial junctional permeability.